This is not meant to discourage, but rather give you realistic view.
Based on number of data points gathered in other threads, average portfolios tend to sell around 2-4% of total images per month. This is no guarantee and individual results will vary a lot based on subject, commercial value, uniqueness and many other factors; some make a lot with very small port, some make very little with huge ports. Never the less, this can help you estimate and judge where you are relative to a generic average port. So with 26 photos your baseline number would be 1 sale (assume 25c) every 3-4 months.
Given all the valid feedback others have provided, the quality of your port is at this point not that great even for average number, which means your sales will probably be worse than anticipated above.

As a hypothetical chance, that can happen yes, but similar logic could be applied to other editorial shots of people or objects, not necessarily right next to the shelter. Person fleeing gang violence can end up on someones street photo shot giving hints to where they are; photo of a house could be used by someone to plan a breakin; photo of a car can be used for theft. It's a trade-off between freedom vs privacy vs security vs risk and its hard to strike the balance at times.
To me the difference is whether one is knowingly and intentionally putting someone else at risk. The best we can do is to try to not harm others while enjoying our hobby/jobs/professions; at the same time I do believe we have to stand for our rights as well (not always, but frequently), else otherwise everything can be taken away in the name of someone elses hypothetical well being. No easy generic answer; just have to make a decision on case by case basis and live with whatever consequences of our decisions.

People sometimes forget that just because something is legal it doesn't mean one should be doing it. On the other hand accidentally snapping random persons image as they walk by the shelter poses rather small additional risk; in some countries almost every car has a video recorder, so such person would appear recorded on them as well.

When it comes to anything dealing with image processing/analysis Adobe (and by extension AS) has much better tech and slew of patents to deal with stuff like this. I wouldn't be surprised if Adobe had proprietary methods of fast image comparisons not available to anyone else.
And just doing quick search it does happen elsewhere, it's just their forums are so horrible (and some agencies don't even let you post anything negative) that it barely gets noticed. Examples from first search on google:
https://forums.adobe.com/thread/2564990
https://forums.adobe.com/thread/2342100
Not defending SS, but naturally being #1 stock site would attract most thieves as well.

This will work first few times; nothing stops thieves from opening new accounts and learning from their mistakes. Whatever solution is, it better be longer term, else this will turn into cat and mouse game with SS being behind.
Until someone writes a simple script and uploads youtube video with directions on how to make fast money from other peoples images. People bypass content security (serial keys) for apps all the time; with images they have greater motivation of actually making real $ from their theft, so I wouldn't underestimate their ability, skills or persistence.

System just searches things based on tags that are similar enough and probably keeps some other relevant information around to link 'related' images (e.g. if 2 images were purchased or viewed in succession by customer). So, no, system doesnt compare image to whole database every time you click

Because its very computationally expensive to compare every image against the database of 250+ million. Doing exact match might be doable, but then a thief just has to modify few pixels to avoid that. Doing approximate match comparisons would use too much cpu/power/time.

While a valid experiment, one thing you also need to take into account is search in native languages based on timezones that are in question. It might be that search for say 'sunset' in English shows image on first page of relevant results, while doing same in chinese , for example, has it buried much further away.